ASTM C231/C231M - Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method

Question 1

“This test method is intended for use with concretes and mortars made with relatively _____ aggregates”

Answer 1

Dense

Question 2

TRUE or FALSE
Pressure method testing is not applicable to concretes made with lightweight aggregates, air-cooled blast-furnace slag, or aggregates of high porosity. In those cases, test method C173 should be used.

Answer 2

True.

ASTM C231 is intended for concretes and mortars made with relatively dense aggregates.

Question 3

RODDING or VIBRATION

A - Concrete with slump less than 1”
B - Concrete with slump between 1” and 3”
C - Concrete with slump greater than 3”

Answer 3

A = Vibrate
B = Vibrate or Rodding
C = Rodding

Question 4

If concrete slump is 2”, what method(s) of consolidation could you use?
Considering the method of consolidation you choose, how many layers of equal ______ do you place into the bowl?

Answer 4

You can consolidate using either
VIBRATION or RODDING method.

If VIBRATING, 2 layers of equal VOLUME
If RODDING, 3 layers of equal VOLUME

Question 5

Before adding concrete to the measuring bowl, what must be done?

Answer 5

Dampen the bowl

Question 6

When rodding “each upper layer, allow the rod to penetrate through the layer being rodded and into the layer below approximately ___ mm [ ___ in.]”

Answer 6

25 mm [1 in]

Question 7

How may times should you rod each layer?

Answer 7

25

Question 8

What is the weight of the mallet used with measures of 14 L [0.5 cu. ft.], or smaller?
What is the weight of the mallet used with measures greater than 14 L [0.5 cu. ft.]

Answer 8

1.25 lbs, +/-0.5 lbs
(for measures 14 L [0.5 cu. ft.], or smaller)

2.25 lbs, +/-0.5 lbs
(for measures greater than 14 L [0.5 cu. ft.])

Question 9

When vibrating, “insert the vibrator at ___ different points for each layer of concrete.”

Answer 9

3

Question 10

“In compacting the final layer, the vibrator shall penetrate into the underlying layer approximately
___ mm [ ___ in.]”

Answer 10

25 mm [ 1 in]

Question 11

TRUE or FALSE
After final consolidation, “the measure must NOT contain a substantial excess or deficiency of concrete. An excess of concrete protruding approximately 9 mm [3/8 in.] above the top of the mold is optimum.

Answer 11

False

3 mm [ 1/8 in.] is optimum

Question 12

TRUE or FALSE
Do not let the vibrator to touch, or rest on the bottom of the measure. It’s okay if the vibrator touches the sides of the measure as long as its not held there.

Answer 12

False

“do not allow the vibrator to rest on or touch the bottom OR sides of the measure”

Question 13

For Vibrator information, C231 references C192/C192M

Per ASTM C192/C192M
“Vibrator frequency shall be at least _____ vibrations per minute while the vibrator is operating in the concrete.”

Answer 13

9000 vibrations per minute

Question 14

For Vibrator information, C231 references C192/C192M

Per ASTM C192/C192M
“Diameter of a round vibrator shall be no more than ____ the diameter of the cylinder mold or ____ the width of the beam or prism mold.”

Answer 14

1/4 the diameter of a cylinder mold

1/4 the width of the beam or prism mold

Question 15

Tamping Rod shall be at least 4 inches greater than ________________, but not be greater than ____ in total length.

Answer 15

The depth of the measuring bowl.

24” in total length

Question 16

The tamping rod should have a diameter of ____ ?

Answer 16

5/8” (+/- 1/16”)

Question 17

The tamping rod is a round, smooth, straight steel rod. The tamping end, or both ends, should be rounded ___ __ ___________ tip of the same _______ as the rod.

Answer 17

TO A HEMISPHERICAL tip of the same DIAMETER as the rod

Question 18

The mallet head is to be made of?
(Note all that apply)

Dense Plastic
Rubber
Wood
Metal
Rawhide

Answer 18

Rubber

Rawhide

Question 19

“After consolidation of the concrete, strike off the top surface by sliding the strike-off BAR across the top flange or rim of the measuring bowl with a ______ motion”

Answer 19

sawing

Question 20

Steps for using a strike-off PLATE
1 - Cover ____ of the top of the bowl with the plate.
2 - Withdraw the plate using a ________ motion
3 - Cover initial ____ of the top of the bowl
4 - Advance the plate forward using a _______ motion
5 - Incline the plate and perform final strokes with the ____ of the plate to produce a smooth surface

Answer 20

1 - two thirds
2 - sawing
3 - two thirds
4 - sawing
5 - edge

Question 21

Strike of BAR to be a flat, straight bar of steel or other suitable metal at least ___ in. thick, ___ in. wide, and ___ in. long

Answer 21

1/8” thick [6 mm]
3/4” wide [20 mm]
12” long [300 mm]

Question 22

1 - How thick must a metal strike-off PLATE be?

2 - How thick must a glass or acrylic strike-off PLATE be?

Answer 22

1/4” - if metal

1/2” - if glass or acrylic

Question 23

Test procedure for a “Type B” meter:

After you have dampened the cover assembly and have clamped it into place, what are your next 4 steps?

Answer 23

1 - close the main air valve
2 - open both petcocks
3 - use the syringe to fill one petcock until water emerges from the opposite petcock
4 - jar the meter

Question 24

Test procedure for a “Type B” meter:

What is the purpose for jarring the meter after water emerges from the opposite petcock as to where you’re filling with the syringe?

Answer 24

to expel air that may be trapped

Question 25

Test procedure for a “Type B” meter: TRUE or FALSE

When you are satisfied that all air has been expelled through the petcock after jarring the meter, you need to close both petcocks.

Answer 25

False, You close the air bleeder valve

Question 26

Test procedure for a “Type B” meter:

What is the next step after jarring the meter and removing trapped air through the petcock?

Answer 26

Close the air bleeder valve on the air chamber

Question 27

Test procedure for a “Type B” meter:

What is the next step after closing the air bleeder valve on the air chamber?

Answer 27

Pump air into the air chamber.

Question 28

Test procedure for a “Type B” meter:

You pump air into the air chamber until the gauge hand is on the _______ pressure line?

Answer 28

Initial

Question 29

Test procedure for a “Type B” meter: TRUE or FALSE

After you finish pumping air to the initial pressure line, allow a few seconds for the compressed air to cool to normal temperature.

Answer 29

True

Question 30

Test procedure for a “Type B” meter:

After pumping in the air, stabilize the gauge hand at the initial pressure line by _______ or _______ air as necessary, then _______ the gauge lightly by hand.

Answer 30

• pumping in
• bleeding out
• tapping

Question 31

Test procedure for a “Type B” meter:

Once air has been pumped in and the the gauge hand is stable at the initial pressure line, what are the next 5 steps, in order.

Answer 31

1 - close both petcocks
2 - open and hold down the main air valve
3 - strike the side of the meter smartly with the mallet
4 - still holding open the main air valve, tap the gauge lightly to stabilize the gauge hand.
5 - record the percentage of air on the gauge